All filters should be replaced periodically. The replacement of filters in an efficient way optimizes machine operation and minimizes wear while minimizing filter costs. In many applications, air intake filters are changed based on a measurement of the pressure drop, filter particulate load, or other measurement of an unambiguous parameter of filter operation.
In consumer applications for light motor vehicles, the use of a measurement of a specific filtration parameter is simply not done due to cost and complexity. In light vehicle manufacture, the filter is simply replaced periodically, with or without a cursory inspection of the filter surface. One important parameter used to judge replacement relates to vehicle mileage. The filter can be simply replaced (e.g.) every 5,000-50,000 miles. This has little relationship to the likely accumulation of particulate on the filter surface because of the differences in environment, maintenance activity and other parameters. Such unscientific filter maintenance can be a problem.
Most automobile filters, when initially placed in service, have very low efficiency. The efficiency of the filter tends to substantially increase during filter life when the filter particulate participates in filtration efficiency. Filtration efficiency may not reach a sufficient level to provide protection to the engine for some weeks after installation. Accordingly, the replacement of the filter in an aggressive maintenance schedule can often result in substantial engine wear because of the low efficiency of clean filters. Filters that remain in the vehicle for extended periods of time can also cause problems related to substantially reduction of power output due to plugged filters, high ΔP and reduced flow rate.
Accordingly, a substantial need exists to obtain a filter that has an initial high efficiency, an improved indicator of useful lifetime, an improved method of maintaining motor vehicles and an improved business method for the retail maintenance of both passenger and fleet vehicles.